Pogba was unable to train with the rest of United's squad on Friday and instead forced to work indoors after suffering what has been described as a "little injury".

It is unclear at this stage if the France midfielder is in danger of missing the trip to Manchester City or when the problem occurred.

United trained at 3pm on Thursday afternoon following their return from Turin where they beat Juventus 2-1 in the Champions League on Wednesday. Manager Jose Mourinho has another training session planned for Saturday.

Alexis Sanchez trained on Friday despite the Chile striker suffering a minor thigh injury against Juventus. Romelu Lukaku has missed United's past two matches against Bournemouth and Juventus through injury but the Belgium striker underwent some light training on Wednesday and Thursday and trained again on Friday.

Mourinho wants to see how Lukaku responds on Saturday before deciding whether to include him in his squad.

Earlier on Friday Mourinho vowed to go toe-to-toe in Sunday’s derby with a Manchester City side that he claims are “untouchable” in terms of the quality of their football and the squad they have built.

But Mourinho lauded the way the Premier League champions have invested their money and the work Pep Guardiola has done since taking charge at the Etihad Stadium in the same summer he was appointed United manager in 2016.

The United manager has expressed frustrations about his own club’s work in the transfer window and was angry at being denied a new centre-half in the summer but he believes City’s success is undeniable, despite the FFP storm engulfing the club.

“If you want to speak about their football potential we can speak and football potential starts with investment. After that, of course, there is a quality of the work, of the organisation, and I think that is untouchable. What is behind [it] I cannot say. In this moment I have only to think about football and to think about football is to think about Manchester City as a football team there.”

Despite Mourinho’s admission of the threat City pose, he is convinced the champions know they will be in for a tough game at the Etihad on Sunday as he prepares to fight fire with fire, embolded by Wednesday’s win away to Juventus and a 2-2 draw at Chelsea.

Asked about the prospect of going toe-to-toe with City, Mourinho said: “We are going to try, I cannot say we are going to be successful in our motivations, in our desire, but we played two difficult matches away against two very good teams, Chelsea and Juventus, and we managed to get good results.

“And even if the good results were not in our pockets, the performances were there, the positive attitude was there so we are going to try but you are right, Manchester City are a very powerful team.”

United will move to within six points of leaders City if they win but Mourinho said he will tell his players to treat the match as a one-off amid concerns the scale of the task will become harder if he discusses it in the context of their season’s prospects.

“If we drew it [the gap] is nine and if we lose it is 12 [points], I don't think that is the way to look at the match,” Mourinho said. “We have to just think about the match, it is difficult enough as an isolated event. If you want to put that match in the context of where we are, where we can be, it becomes even more difficult so I want to see it as an isolated event. I want to play it as an isolated match, it is a difficult match against a difficult team but they think it is difficult match for them.”

Mourinho has been impressed by the spirit his players have shown to come from behind in games against Newcastle, Chelsea, Bournemouth and Juventus but he claimed there will come a point where his team cannot recover from poor starts.

It's been a testing week for Manchester City off the pitchCredit:
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“We can go to the other side, why we always concede before opponents,” Mourinho said. “If you want to go in a positive way, it is easy to feel a team that does not give up, always find a way to fight back, sometimes changing results, sometimes not, but we are a team that has that collective spirit to fight back but is not always possible.

“If we keep conceding goals before the opponents there will be a day where we cannot come back so we have to grow up in our approach, because it is clear the team is growing up, but we have to grow up in our compactness and start matches well.

“Against Juventus, it happened, we conceded the goal in minute 60 or something like that and we had a good start. In the first 15 or 20 mins we were totally in control.”